1. Field of the Invention
This invention relates generally to viewing scopes and more particularly to an endoscope that facilitates three-dimensional viewing.
2. Description of Related Art
Endoscopes have attained great acceptance within the medical community in connection with a number of procedures. This acceptance exists because endoscopes provide a means for performing procedures with minimal patient trauma while enabling a physician to view directly the internal anatomy of a patient. Over the years a number of endoscopes have been developed and have been categorized according to specific applications. Many have specific names including arthroscopes, cystoscopes, proctoscopes, laparoscopes and laryngoscopes. Industrial endoscopes are often called borescopes.
In whatever specific form, an endoscope generally comprises an objective lens system at the distal end of the endoscope that forms an image of an object. With medical endoscopes the object generally is within a patient in some environmental media such as air, water, a saline solution or the like. Industrial endoscopes image objects that may be located in a remote enclosed volume. An eyepiece or ocular system at the proximal end presents the image for viewing visually, electronically or otherwise externally of the patient or enclosed volume. An image transfer system intermediate the objective and the eyepiece systems transfers the image produced by the objective lens system to the eyepiece system.
Significant efforts have been undertaken to improve the optical designs of these endoscopes with attention at various times directed to individual ones of the constituent optical systems. The above-identified application Ser. No. 08/883,216 describes one system with an objective lens that facilitates the design of endoscopes that produce images with low distortion. Other efforts have been directed to improving the display of such an image.
Typically endoscopic displays are monoscopic or two-dimensional that, as known, do not facilitate depth perception. Yet in many modalities depth perception would be advantageous if available. For example, a three-dimensional view would simplify a surgeon's task in bringing two implements of identical shape but different sizes together in predictable and repeatable manner. It is very difficult to achieve that feat with a two-dimensional image.
The efforts in developing displays to improve depth perception have taken different approaches. In accordance with one approach, direct viewing devices produce stereoscopic images. For example, in U.S. Pat. No. 3,520,587 to Tasaki et al. two elongated flexible optical fiber systems with independent objective lenses focus images to be inspected. The images are then transmitted to a proximal end through light bundles that are incident to the respective objective lens systems to form a parallax angle that creates a visual perception of a three-dimensional object.
U.S. Pat. No. 4,061,135 to Widran et al. discloses a binocular endoscope in which a non-distorting, high resolution, optical system utilizing long path length lenses conveys the image of a viewed object onto two optical paths. Prisms and other optical elements provide folded optical paths to two lenses in binocular eye pieces to produce an image with depth perception.
U.S. Pat. No. 4,386,602 to Sheldon et al. discloses an intracranial surgical operative apparatus. A pair of endoscopes extend along converging endoscope axes. When a surgeon views an object through the two eyepieces, the surgeon perceives a stereoscopic or three-dimensional image.
U.S. Pat. No. 4,836,188 to Berry discloses an instrument for providing stereoscopic viewing of a body cavity. A head mounted unit includes optical elements in a folded optical path that convey an image to eyepieces. Light reflected from the object is split into two beams that are directed through the eyepieces to the eyes of the viewing surgeon.
U.S. Pat. No. 4,834,518 to Barber discloses another instrument for enabling a surgeon to visualize a three-dimensional image. This instrument uses fiber optics to convey images to left and right proximal lens systems disposed in eyepieces from distal left and right objective lens systems. The distal objective lens systems have converging optical axes to enable depth perception of an object.
In accordance with another development approach, a pair of images are displayed on a television monitor screen so a surgeon can "fuse" the images into a single image with perceived depth. For example, in U.S. Pat. No. 4,429,328 to Jones, Jr. et al. apparatus produces a three-dimensional illusion through the sequential display of images viewed alternatively from different points of origin at a rate which allows the eye to fuse the image. The maximum effect is achieved when the points of origin are vertically aligned with respect to one another and displaced from one another by a distance less than the normal interoccular distance.
U.S. Pat. No. 4,528,587 to Jones, Jr. discloses apparatus in which first and second video cameras view an object from different points of origin. A switching device alternately couples frames from the two video cameras to produce a composite picture on a viewing device, such as a television set. The individual who views the image relies on image fusion to produce an image with perceived depth.
U.S. Pat. No. 4,656,508 to Yokota discloses an endoscope in which light produces a lattice-shaped light pattern on the object. An objective lens system directs the images to an image sensor that produces electrical signals to produce an image. A control synchronizes with the operation of the illumination light supply to process the resulting image with a three-dimensional effect.
U.S. Pat. No. 4,862,873 to Yajima et al. discloses apparatus with first and second optical guides. During alternate operating intervals light is transmitted through one optical guide with the reflected image being transferred to the other. During the next interval the functions of the two optical guides reverse. This produces an alternating image display at a speed that provides a perceived continuity of image. A video monitor with shielded filters synchronized with the light switching intervals displays the image.
U.S. Pat. No. 4,926,257 to Miyazaki also discloses a stereoscopic endoscope. A common light supply illuminates two sets of optical fibers that convey images from two separate objective lenses. The images are multiplexed into a electronic system for display through a filtered output that operates in synchronism with the switching of the optical paths.
In accordance with a third approach, an endoscope produces images for display on a virtual reality viewing device. For example, U.S. Pat. No. 4,651,201 to Schoolman discloses a stereoscopic endoscope. A sheath for insertion in the body of a patient contains a pair of image guides and an illumination light guide, preferably formed of optical fibers for flexibility. The image guides optically connect to a stereoscopic viewer for three-dimensional viewing of the site in the body. In one embodiment the viewer includes couplings for attaching miniaturized video cameras that are in turn connected to a stereoscopic video display mounted in headgear.
U.S. Pat. No. 5,647,838 to Bloomer discloses a holder that supports two monoscopic endoscopes in a distally convergent alignment to view an object along axes at a predetermined convergent angle. Video cameras attach to the proximal ends of each endoscope. A multiplexer then conveys the signals from the two cameras to the three-dimensional viewing devices. The glasses in such a viewing device provides an image which the individual perceives in three dimensions.
Apparatus incorporating the first approach of direct viewing are often cumbersome to use. The devices become physically large as they must have eyepieces conformed to align with an individual's eyes. Only direct viewing is available by the person handling the endoscope. There is no way to provide a remote image. Consequently for these and other reasons this approach has not gained wide favor within the medical community.
Stereoscopic endoscopic devices according to the second approach have also failed to gain wide-spread acceptance. The required electronics increases costs. Individuals using these devices during long medical procedures have reported some eye fatigue apparently produced by the images switching.
The third approach has produced more promise but as yet has not found any commercially acceptable embodiments. The structure in the Bloomer patent, for example, relies upon the holder to establish a divergent angle physically. Consequently the endoscopic structure widens as it extends proximally and can limit the distance by which the endoscope can enter a body without requiring an otherwise unnecessary large entry site. The Schoolman patent suggests an endoscope with parallel endoscope axes that would minimize the entry site. The disclosure seems to suggest attaching video cameras to each of the eyepieces thereby to reproduce what would otherwise be seen by direct viewing. Moreover, the Schoolman patent indicates a preference for a fiber optic image guide. Experience shows that the spatial and contrast resolutions provided by such fiber optic systems does not provide an image with sufficient definition for many applications.